Ms. Gechtoff made a quick and substantial impression in San Francisco, where she had arrived in 1951, a time when the Bay Area art scene was bubbling. An early oil, “Self Portrait,” made in 1954 when she was still in her 20s, is now in the collection of the Smithsonian Institution. That same year she was represented in a group show of young painters at the Guggenheim Museum in Manhattan.

She was also becoming well known in the California art world, with solo exhibitions at outlets like the de Young Museum in San Francisco and the Ferus Gallery in Los Angeles, both in 1957.

But in 1958 she and her husband, the artist James Kelly, whom she had married in 1953, decamped for New York. Though she was identified with the Abstract Expressionist genre her whole life — her early work has been the focus of a rediscovery recently — she experimented with styles and materials throughout her career.

In 1976, when Hilton Kramer of The New York Times called her “one of the most gifted artists of her generation,” he was reviewing a show of her pencil drawings.

Sonia Alice Gechtoff was born on Sept. 25, 1926, in Philadelphia, into a family with art in its genes. Her father, Leonid, was a painter, and her mother, Etya, was a gallery owner and manager.

Ms. Gechtoff received a bachelor of fine arts degree from the Philadelphia Museum School of Art (now the University of the Arts) in 1950. After moving to San Francisco, she largely abandoned figurative work in favor of the abstract.

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Ms. Gechtoff working on a painting with a palette knife in her Canal Street studio in Manhattan in the early 1960s.

It was a time of envelope pushing among artists, which included experimenting with ways to apply paint other than with a brush. (Jackson Pollock’s drip-painting period began in the mid-1940s.) Ms. Gechtoff started working with the palette knife.

“The palette knife has been used for ages to mix and move paint, but until Sonia’s generation, the brush ruled as far as the mechanism to apply paint to canvas,” Marshall N. Price, the Nancy Hanks curator of modern and contemporary art at Duke University’s Nasher Museum of Art, wrote in an email. “Sonia refined her palette knife technique, and by the late 1950s the slashing marks, often applied in a vortexlike way, were a hallmark of her work.”

Reviewing Ms. Gechtoff’s first New York exhibition after her move east, a 1959 show at the Poindexter Gallery, the critic Dore Ashton wrote in The Times that the technique had produced “a surface similar to the overlapping feathers of a wet bird.”

However it was described, it made Ms. Gechtoff stand out in a genre that was largely male. A 1961 article in The Times about a brewing boycott by artists, in response to fire-code restrictions that threatened their lofts, said that “some big box-office names” had pledged to support the strike. It then listed 21 of those names, among them Robert Motherwell, Jasper Johns and Willem de Kooning. Ms. Gechtoff was the only woman on the list.

Ms. Kelly said that having two artists as parents made for a “home environment filled with creativity” for her and her brother, Miles, a musician who also survives their mother. Artists and other friends of their parents were always stopping by to talk art, politics, film and more.

“She was not an average mother in that we as her children learned to curse from her and to never hold back on our opinion,” Ms. Kelly said by email. “I remember her cursing at the TV whenever Lyndon Johnson was on talking about the Vietnam War. I remember Mom going to Washington to protest the war.”

Ms. Gechtoff was still displaying that spiritedness late in life. A 2011 article about her in Art in America magazine began, “Tough, straight-talking abstract painter Sonia Gechtoff is currently being rescued from ill-deserved obscurity.”

The “ill-deserved obscurity” had come gradually. Ms. Gechtoff continued to produce new work throughout her life, and to experiment. In a 1983 exhibition at the Gruenebaum Gallery, Michael Brenson wrote in The Times, she veered from abstraction and “put her mastery of color and composition in the service of identifiable subjects,” including the Brooklyn Bridge and the temples at Paestum in Italy.

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“Messenger,” 2017, acrylic on canvas.CreditAnita Shapolsky Gallery

“She finds the angles and scale that reveal the grandeur of the ancient stone and modern steel,” Mr. Brenson wrote. “And she illuminates her blocks of color with her own muted yet intense light.”

Her name, though, became less and less familiar as the art world moved on — until recently, when Abstract Expressionism and female artists both began to be rediscovered.

She was among 18 artists featured in “Bella Pacifica: Bay Area Abstraction 1946-1963, a Symphony in Four Parts,” a 2011 exhibition at four galleries in New York. She was one of 12 in “Women of Abstract Expressionism,” an exhibition organized by the Denver Art Museum in 2016 that later toured.

Mr. Kelly, her husband, died in 2003. Her children are her only immediate survivors. Ms. Gechtoff had lived in Greenwich Village.

In the 2011 interview with Art in America, Ms. Gechtoff talked about the female forms in her abstract work from the 1950s, playing down the idea that they were a feminist statement.

“I wasn’t the least bit interested in feminist art, and I still am not,” she said. “We were feminist before the feminists came along.”

A version of this article appears in print on , on Page B6 of the New York edition with the headline: Sonia Gechtoff, Abstract Expressionist, Dies at 91. Order Reprints | Today’s Paper | Subscribe